From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Preliminary report on the B.T.H. Magneto F.M.6.
| Identifier | WestWitteringFiles\F\February1921\ Scan95 | |
| Date | 10th December 1920 | |
| R.R. 235A (100 T) (S.H. 798, 10-12-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2947 EFC. COPY. 91286. P.A.65. PRELIMINARY REPORT ON B.T.H. MAGNETO F.M.6. This is a very small machine, compared with the others, with a weight of 10.25 lbs. It has only one magnet. The armature is enclosed in an aluminium body with laminated pole shoes, cast in the sides. Between these main pole-shoes and the armature is a brass sleeve, or cylinder, which has laminated segments cast in the sides, 180° apart, and which fits closely in the pole shoe tunnel. This sleeve is fixed to the cam ring so that the polar segments are moved backwards and forwards with the control lever. It is a similar idea to that in practice on the B.C.6 Watford, the armatures also being about the same size, but there is this difference, that whereas in the Watford case there is an air gap between the movable sleeve and the pole shoe tunnel, the sleeve being located at either end, in the B.T.H. magneto the sleeve is a sliding fit in the pole shoe tunnel and located by the surface of the tunnel itself. The contact breaker lever has the appearance of having been balanced by being drilled out towards the contacts points, while the cam end is made bulky. Americanite is used throughout instead of mica and fibre. It has a continuous cam formed by grinding out the inside of a thick steel ring, which gives similar periods of make to that of a magneto with long ordinary cams. Contd. | ||